1. Technical Field
The present invention relates to a copper alloy, which comprises hard particles and optionally solid lubricants, the use of said copper alloy for a bearing, a bearing made of said copper alloy, and a method for producing said bearing.
2. Related Art
Lead-free copper alloys comprising iron and phosphorus are known as high-performance materials in electrical engineering.
For instance, US 2009/0010797 A1 discloses a strip made of a copper alloy, which is essentially an alloy of the Cu—Fe—P type comprising 0.01 to 3.0% by weight of Fe and 0.01 to 0.3% by weight of P, and may further comprise small amounts of Zn, Sn, Mn, Mg and Ca. The aim is to provide a material having high electrical conductivity, high strength and good flexibility, for instance for use in circuit boards.
US 2006/0091792 A1 discloses thin films made of a copper alloy, which comprises Fe and P and is used in flat screens. Furthermore, a sputter substrate for the production of corresponding thin films is provided.
Furthermore, the material data sheet “CuFe2P” of the German Copper Institute (Deutsches Kupferinstitut) as well as the data sheet regarding “Wieland-K65” describe corresponding copper alloys for electronic components.
However, copper alloys are also widely used in bearing materials and sliding elements e.g. in the form of “bearing bronzes”. The wear resistance of these alloys can be increased e.g. by precipitation hardening in an alloy system specifically selected for this purpose or by adding hard materials.
In this regard, DE 10 2007 049 383 A1 describes a composite material, in particular a friction composite material, which comprises a substrate material of a steel material and a layer of a copper alloy. The aim is to provide a material that can easily be formed into a molded part and comprises a wear-resistant friction layer. The wear resistance is achieved in that the copper alloy of the layer consists of a hardenable copper alloy e.g. CuNiSi, CuNiSiMg, Cu—Cr, Cu—Fe, Cu—(Fe, Co, Ni)—P, CuBe or CuMg. As substrate material, carbon steel, heat-resistant steel, case-hardened steel or nitrided steel can be used for instance. Furthermore, a method for producing the composite is described, in which the copper alloy is roll-plated as a film onto the substrate material and goes through various heat treatments. The wear-resistant surface is created only after forming the composite into a friction body by precipitation hardening.
DE 10 2005 014 302 A1 describes a method for producing a sliding bearing as well as a sliding bearing as such with the object of providing particularly favorable sliding surfaces. This is achieved by etching processes, in which specific phases are selectively dissolved out of the material of the sliding surface, and other phases remain on the surface. For this purpose, copper multicomponent alloys having at least two different phase constituents in the structure are used. These phases can be formed via precipitation. Copper aluminum multicomponent bronzes, which can contain Fe, Ni, Mn, Zn and Si, as well as CuAl13Fe4, 5CoMn, CuAl15Fe4, 5CoMn and CuAl10Ni5Fe4 are stated as examples of suitable materials. Depending on the choice of acid for etching, it can be determined whether harder or softer phases remain on the surface, which allows an adjustment to the intended use of the sliding element. The created etching structure further allows that a wear-reducing lubricant reservoir can be formed.
EP 0 962 541 A1 describes a sintered, copper-based sliding material which is characterized by the addition of hard material particles of medium and high hardness. Pure copper or copper alloys are suggested as basic material. Cu—Ag base alloys or Cu—Pb—Ag base alloys can be used as copper alloys. Further, these alloys can comprise up to a total of 50% by weight of the following additives: Ni, Sn, P, Al, Si, Bi, Mn, Zn, Fe and Sb. The sliding material achieves good sliding properties and, at the same time, good processability by the specific addition of particles of great hardness from the group of metallic oxides, borides, carbides and nitrides and particles of medium hardness such as e.g. Fe3P, Fe2P, Fe3B, TiSi2, ZrSi2 or NiP. The particles of high hardness are added in an amount of 0.01 to 15% by weight and with average particle diameters of 0.5 μm or more. The particles of medium hardness are added in an amount of 0.5 to 20% by weight and with average particle diameters of 50 μm or less.
The bearing material itself is produced by mixing a copper-containing powder, which was created e.g. by atomization, with the hard material particles, by subsequent spreading on a steel strip and sintering.
WO 2008/140100 A1 discloses a lead-free, copper-based sliding material which comprises an Ag—Bi eutectic and further the elements Ni, P, Zn as well as 1 to 10% by weight of hard material particles from the group of Fe3P, Fe2P, FeB, NiB and AlN with average grain sizes of 1.5 to 70 μm.